JP2002081350A - Air/fuel ratio controller of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the exhausted amount of harmful air pollutants such as hydrocarbon, carbon monoxide, and nitrogen carbide by reducing a variation in air/fuel ratio and lowering emission and improve a fuel consumption by preventing an excess fuel from being fed to an internal combustion engine in the air/fuel ratio controller of the internal combustion engine. SOLUTION: This air/fuel ratio controller comprises a canister temperature detection means for detecting a canister temperature state in a canister, an engine temperature detection means for detecting the engine temperature state of the internal combustion engine, and a control means for calculating the adsorbed amount of evaporated fuel in the canister based on a canister temperature from the canister temperature detection means and an engine temperature from the engine temperature detection means and changing an air/fuel ratio control constant according to the adsorbed amount of the evaporated fuel thus calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air-fuel ratio control device for an internal combustion engine, and more particularly to an air-fuel ratio control device for an internal combustion engine that controls the air-fuel ratio according to the amount of fuel vapor adsorbed in a canister.

[0002]

2. Description of the Related Art In a vehicle, evaporated fuel (volatile fuel) leaking from a fuel tank into the atmosphere contains a large amount of hydrocarbons (HC) and is one of the causes of air pollution.
Various techniques are known to prevent this since it leads to fuel loss. As a typical example, activated carbon as an adsorbent housed in a canister is made to adsorb and hold the evaporated fuel (evaporation) from the fuel tank, and during operation of the internal combustion engine, the adsorbed and held evaporated fuel is purged (separated). ) To supply the purge gas, which is the evaporated fuel thus purged, to the internal combustion engine.

[0003] In this case, between the evaporative passage communicating with the fuel tank and the purge passage communicating with the intake system of the internal combustion engine, fuel vapor from the fuel tank is adsorbed and held on activated carbon as an adsorbent, and the atmospheric pressure is maintained. A canister is provided for purging the adsorbed and evaporated fuel and introducing a purge gas to the internal combustion engine. A purge valve is provided in the middle of the purge passage. The purge valve is operated in accordance with the operation state of the internal combustion engine to control the purge amount, which is the flow rate of the purge gas to the internal combustion engine, and to control the air-fuel ratio. The activated carbon housed in the canister has a property of causing an endothermic reaction at the time of the purge reaction of the vaporized fuel adsorbed and held, thereby lowering the temperature, that is, the characteristic of lowering the internal temperature of the canister.

An air-fuel ratio control device for an internal combustion engine is disclosed in, for example, Japanese Patent Application Laid-Open No. 5-133289. In this publication, a temperature sensor is provided in a canister, and air-fuel ratio control based on a learned value or air-fuel ratio control based on a map is performed in accordance with the canister temperature state.

[0005]

However, in the conventional air-fuel ratio control device, it is difficult to directly measure the amount of fuel vapor adsorbed in the canister, and the air-fuel ratio control device is based on the amount of vapor fuel adsorbed. Since the air-fuel ratio control could not be performed, the evaporated fuel affected the control of the internal combustion engine, and the air-fuel ratio could not be controlled with high accuracy. As a result, emissions of harmful air pollutants such as hydrocarbons (HC), carbon monoxide (CO), and nitrogen carbide (NOx) increase, and excess fuel is supplied to the internal combustion engine, resulting in poor fuel economy. There was an inconvenience.

[0006]

SUMMARY OF THE INVENTION In order to eliminate the above-mentioned disadvantages, the present invention provides a fuel tank which is provided between an evaporation passage communicating with a fuel tank and a purge passage communicating with an intake system of an internal combustion engine. A canister that adsorbs and holds the evaporated fuel from the adsorbent to the adsorbent, purges the adsorbed and held evaporated fuel by introducing air, and supplies a purge gas to the internal combustion engine, and provides a purge valve in the middle of the purge passage. In an air-fuel ratio control device for an internal combustion engine that controls a purge amount, which is a flow rate of a purge gas to the internal combustion engine, by operating the purge valve according to an operation state of the engine, a canister temperature detection for detecting a canister temperature state in the canister Means for detecting the temperature of the engine of the internal combustion engine. Calculating the amount of fuel vapor adsorbed in the canister based on the canister temperature from the means and the engine temperature from the engine temperature detecting means, and changing the air-fuel ratio control constant according to the calculated amount of fuel vapor adsorbed. Control means for performing the control.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention estimates the amount of fuel vapor adsorbed in a canister based on the canister temperature and the engine temperature, and controls the air-fuel ratio of the internal combustion engine in accordance with the estimated vapor fuel adsorbed amount. As a result, air-fuel ratio control can be performed accurately, air-fuel ratio fluctuations are reduced, emissions are reduced, and emissions of harmful air pollutants such as hydrocarbons, carbon monoxide and nitrogen carbide are reduced. By preventing excess fuel from being supplied to the internal combustion engine, fuel efficiency can be improved.

[0008]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing an embodiment of the present invention; 1 to 3 show a first embodiment of the present invention. 2, 2 is an internal combustion engine mounted on a vehicle (not shown), 4 is an intake manifold, 6
Is an exhaust manifold, 8 is a throttle body, 10 is an intake pipe, 12 is a fuel injection valve, 14 is a fuel tank, 16 is an air-fuel ratio control device, and 18 is an evaporative fuel control mechanism.

An evaporation passage 20 communicating with the fuel tank 14
Between the purge passage 22 communicating with the intake manifold 4 of the intake system of the internal combustion engine 2, the evaporated fuel from the fuel tank 14 is adsorbed and held, and the adsorbed and held evaporated fuel is purged by introducing air. A canister 24 for supplying a purge gas to the internal combustion engine 2 is provided. Activated carbon as an adsorbent for adsorbing and holding the fuel vapor from the fuel tank 14 is provided in the canister 24. This activated carbon has a property of causing an endothermic reaction at the time of purging (leaving) the vaporized fuel adsorbed and held, thereby lowering the temperature, that is, the characteristic of lowering the internal temperature of the canister 22.

In the middle of the evaporation passage 20, the fuel tank 1
An evaporation valve 26 for controlling the amount of fuel vapor (evaporation) from the fuel tank 4 to the canister 24 is provided. Purge passage 2
2, a purge valve 2 for controlling a purge amount, which is a flow rate of a purge gas from the canister 24 to the internal combustion engine 2.
8 are provided.

A canister temperature sensor 30 is provided in the canister 24 as canister temperature detecting means for detecting a canister temperature state which is an internal temperature in the canister 24. The internal combustion engine 2 includes, as an engine temperature detecting means for detecting an engine temperature state of the internal combustion engine 2,
For example, an intake air temperature sensor 32 that is attached to the intake pipe 10 and detects the temperature of intake air is provided.

The fuel injection valve 12, the evaporation valve 26, the purge valve 28, the canister temperature sensor 30, and the intake temperature sensor 32 are connected to a control means 34.

The control means 34 includes an input section 34A, an output section 34B, a timer 34C, and a control map (not shown) of the stored air-fuel ratio control. An input section 34A of the control means 34 includes a canister temperature sensor 30
And an intake air temperature sensor 32, a vehicle speed sensor 36, an engine speed sensor 38, a negative pressure (boost) sensor 40 for detecting an engine load, a throttle opening degree sensor 42, an outside air temperature sensor 44, and an engine cooling water. Temperature sensor 46
, The oxygen concentration detection sensor 48, the intake air amount sensor 50, and other sensors are in communication. The output part 34B of the control means 34 includes the fuel injection valve 12 and the evaporation valve 26.
And the purge valve 28 are in communication.

The control means 34 operates the purge valve 28 in accordance with the operation state of the internal combustion engine 2 to control the purge amount, which is the flow rate of the purge gas to the internal combustion engine 2, and also outputs the signal from the canister temperature sensor 30 to the canister. The amount of adsorbed fuel vapor in the canister 24 is calculated based on the temperature (C) and the intake air temperature (I) which is a signal from the intake air temperature sensor 32, and the air-fuel ratio is calculated according to the calculated amount of adsorbed fuel vapor. This is to change the control constant. In this case, as shown in FIG. 3, the amount of adsorbed fuel vapor is equal to the reduced temperature change value ΔT of the canister 24 calculated from the change amount of the canister temperature (C) and the change amount of the intake air temperature (I). It is calculated (thrusting side) based on this. In detecting the temperature of the internal combustion engine 2, the ambient temperature of the canister 24 or the outside air temperature can be used instead of the intake air temperature.

When the calculated amount of adsorbed fuel vapor is larger than the set value A, the control means 34 changes the air-fuel ratio control basic value itself, while the calculated amount of adsorbed fuel vapor becomes equal to the set value A. When it is smaller than the above, a correction value is added to the air-fuel ratio control basic value. In this case,
The determination as to whether the calculated amount of adsorbed fuel vapor is larger than the set value A is performed, for example, by setting 70% of the working capacity (operable capacity) of the canister 24 to the above-mentioned set value A.
The calculation is performed depending on whether the calculated amount of adsorbed fuel vapor is 70% or more or 70% or less.

The control means 34 decreases the fuel injection amount when the calculated adsorbed amount of fuel vapor is larger than the set value A, and decreases the fuel injection amount when the calculated adsorbed amount of fuel vapor is smaller than the set value A. This is to increase the fuel injection amount.

Next, the operation of the first embodiment will be described with reference to the flowchart of FIG.

When the program of the control means 34 starts (step 102), various data are taken in.
Vehicle speed, engine speed, negative pressure, throttle opening, outside air temperature,
Information such as the intake air temperature (I1), engine cooling water temperature, oxygen concentration, intake air amount, canister temperature (C1), etc. is fetched (step 104), and it is determined from the fetched information whether the evaporative purge is in progress (step 104). 106).

Then, if this step 106 is YES,
When the evaporative purge is being performed, the timer 34C is started (step 108), and after a lapse of a predetermined time (for example, 30 seconds), the timer 34C is ended (step 110). Information such as the number of revolutions, negative pressure, throttle opening, outside air temperature, intake air temperature (I2), engine cooling water temperature, oxygen concentration, intake air amount, canister temperature (C2), and the like are captured (step 112). It is determined from each information whether the evaporative purge is continuing (step 114).

If step 114 is YES and the evaporative purge is being continued, the amount of fuel vapor adsorbed in the canister 24 is calculated based on the intake air temperature (I) and the canister temperature (C) that have been taken in (step C). 116). That is, the reduced temperature change value ΔT of the canister 24 is obtained by ΔT = {(C2−C1) − (I2−I1)} × a. Here, a is a temperature correction coefficient. Then, as shown in FIG. 3, the amount of adsorbed fuel vapor in the canister 24 is calculated (estimated) based on the obtained reduced temperature change value ΔT.

Next, it is determined whether or not the calculated adsorbed amount of fuel vapor in the canister 24 is larger than a set value A (step 118). This is to correct the air-fuel ratio control of the internal combustion engine 2 together with the stored control map based on the calculated adsorption amount based on whether the adsorption amount of the evaporated fuel is larger than the set value A. is there.

If the determination in step 118 is YES and the calculated adsorbed amount of fuel vapor in the canister 24 is larger than the set value A, the air-fuel ratio control basic value itself is changed or the fuel injection amount is changed. Is reduced to change the air-fuel ratio control (step 120). This change of the air-fuel ratio control has several base maps for determining the fuel injection amount based on the engine cooling water temperature, the engine load, etc. in the control of the internal combustion engine 2. When it is larger than A, the control constant of the basic base map of the air-fuel ratio control is changed.

On the other hand, if the determination in step 118 is NO and the amount of adsorbed fuel vapor in the canister 24 is smaller than the set value A, a correction value is added to the air-fuel ratio control basic value, or the fuel injection is performed. The amount is increased to correct the air-fuel ratio control (step 122). The correction of this air-fuel ratio control is
Without changing the basic air-fuel ratio control base map,
In the same map, for example, the oxygen concentration detection sensor 4
8, the control constant is corrected.

In the case of NO in step 106, in the case of NO in step 114, and in steps 120 and 1,
After the processing in step S22, the program ends (step 1).
24).

As a result, the amount of adsorbed fuel vapor in the canister 24 is calculated based on the canister temperature (C) from the canister temperature sensor 30 and the intake temperature (I) from the intake temperature sensor 32. By changing the air-fuel ratio control constant in accordance with the amount of fuel vapor adsorbed, the amount of fuel vapor adsorbed in the canister 24 can be estimated, and the estimated amount of fuel vapor adsorbed is used as the air-fuel ratio of the internal combustion engine 2. The air-fuel ratio control can be performed by reflecting the amount of the evaporated fuel reflected in the control, whereby the air-fuel ratio control can be performed with high accuracy, the air-fuel ratio fluctuation is reduced, and the emission is reduced. To reduce the emission of air pollutants such as hydrocarbons, carbon monoxide, and nitrogen carbide, and to improve fuel economy by eliminating the need to supply extra fuel to the internal combustion engine 2. It can be.

When the calculated adsorbed amount of the evaporated fuel is larger than the set value A, the air-fuel ratio control basic value itself is changed. On the other hand, when the calculated adsorbed amount of the evaporated fuel is smaller than the set value A, the air-fuel ratio becomes empty. Since the correction value is added to the basic value for fuel ratio control, the control amount of the air-fuel ratio is changed according to the amount of adsorption of the evaporated fuel, and the air-fuel ratio fluctuation becomes large due to the control delay. Without consuming
It can contribute to purification of exhaust gas and improvement of fuel efficiency.

When the calculated adsorbed amount of fuel vapor is larger than the set value A, the fuel injection amount is reduced.
When the calculated amount of adsorbed fuel vapor is smaller than the set value A, the fuel injection amount is increased. Therefore, the control amount is changed according to the magnitude of the amount of adsorbed fuel vapor, and the air-fuel ratio fluctuation is increased due to control delay. It is possible to contribute to purification of exhaust gas and improvement of fuel efficiency without becoming unnecessary or consuming extra fuel.

FIG. 4 shows a second embodiment of the present invention.

In the following embodiments, the parts having the same functions as those in the first embodiment will be described with the same reference numerals.

The features of the second embodiment are as follows. That is, the control unit 34 controls the amount of purge to the internal combustion engine 2 based on the calculated amount of adsorbed fuel vapor to prevent the fuel vapor control mechanism 18 from breaking through.

In the second embodiment, as shown in FIG. 4, when the program of the control means 34 is started (step 202), various kinds of data are taken in as vehicle speed, engine speed, negative pressure, throttle opening, outside air. Information such as temperature, intake air temperature (I1), engine cooling water temperature, oxygen concentration, intake air amount, and canister temperature (C1) is fetched (step 204), and it is determined whether or not the evaporative purge is being performed based on the fetched information. (Step 206).

Then, if this step 206 is YES,
If the evaporative purge is being performed, the timer 34C is started (step 208), and after a predetermined time (for example, 30 seconds), the timer 34C is turned off (step 210). Information such as the number of revolutions, negative pressure, throttle opening, outside air temperature, intake air temperature (I2), engine cooling water temperature, oxygen concentration, intake air amount, canister temperature (C2), etc., are captured (step 212). It is determined from each information whether the evaporative purge is continuing (step 214).

If step 214 is YES and the evaporative purge is being continued, the amount of fuel vapor adsorbed in the canister 24 is calculated based on the intake air temperature (I) and the canister temperature (C) that have been taken in (step C). 216). That is, the reduced temperature change value ΔT of the canister 24 is obtained by ΔT = {(C2−C1) − (I2−I1)} × a. Here, a is a temperature correction coefficient. Then, as shown in FIG. 3, the amount of adsorbed fuel vapor in the canister 24 is calculated (estimated) based on the obtained reduced temperature change value ΔT.

Next, it is determined whether or not the calculated amount of adsorbed fuel vapor in the canister 24 is larger than a set value A (step 218).

If this step 218 is YES and the calculated adsorbed amount of fuel vapor in the canister 24 is larger than the set value A, the air-fuel ratio control basic value itself is changed or the fuel injection amount is changed. To change the air-fuel ratio control and increase the purge amount (step 22).
0).

On the other hand, if step 218 is NO and the adsorbed amount of the evaporated fuel in the canister 24 is smaller than the set value A, a correction value is added to the air-fuel ratio control basic value, or the fuel injection is performed. The amount is increased to correct the air-fuel ratio control, and the purge amount is decreased (step 222).

In the case of NO in step 206, in the case of NO in step 214, and in steps 220 and 2,
After the processing in step S22, the program ends (step 2).
24).

As a result, the amount of fuel vapor adsorbed in the canister 22 is calculated based on the canister temperature (C) from the canister temperature sensor 30 and the intake air temperature (I) from the intake air temperature sensor 32. By changing the air-fuel ratio control constant according to the amount of adsorbed fuel vapor and controlling the amount of purge to the internal combustion engine 2, the amount of fuel vapor adsorbed in the canister 24 can be estimated. The absorbed amount of the evaporated fuel is reflected in the air-fuel ratio control of the internal combustion engine 2, and the air-fuel ratio control can be performed based on the absorbed amount of the evaporated fuel, whereby the air-fuel ratio control can be performed with high accuracy. The air-fuel ratio fluctuation is reduced to reduce the emission of air pollutants such as hydrocarbons, carbon monoxide and nitrogen carbide, and the fuel is prevented from being supplied to the internal combustion engine 2 by the excess fuel. It is possible to improve, also,
The estimated adsorption amount of the evaporated fuel is reflected in the purge control,
The evaporative purge amount is adjusted so that the working capacity of the evaporative fuel control mechanism 18 does not exceed a predetermined ratio, the breakthrough of the evaporative fuel control mechanism 18 is prevented, and the capacity of the evaporative fuel control mechanism 18 is effectively used. In addition, the divergence of the fuel vapor can be prevented.

Since the purge amount is controlled in accordance with the amount of fuel vapor adsorbed in the canister 24, overflow of the fuel vapor from the canister 24 can be prevented.

Further, when the calculated amount of adsorbed fuel vapor is larger than the set value A, the purge amount is increased. On the other hand, when the calculated amount of adsorbed fuel vapor is smaller than the set value A, the purge amount is decreased. Thus, it is possible to maximize the adsorption capacity of the canister 24.

In the present invention, the adsorbed amount of the evaporative fuel as a test piece is measured directly at a place where the evaporative fuel is averagely adsorbed in the canister by a measuring instrument at a standstill or the like, and It is also possible to estimate the total amount of adsorption based on the amount of adsorption measured as a test piece. Thus, since the amount of adsorption is directly measured, the amount of adsorption can be estimated more accurately, and a small amount of adsorption is measured, so that a large-scale structure can be eliminated.

[0042]

As apparent from the above detailed description, according to the present invention, the canister temperature detecting means for detecting the canister temperature state in the canister is provided, and the engine temperature detecting means for detecting the engine temperature state of the internal combustion engine is provided. Calculating the amount of fuel vapor adsorbed in the canister based on the canister temperature from the canister temperature detecting means and the engine temperature from the engine temperature detecting means, and controlling the air-fuel ratio according to the calculated amount of fuel vapor adsorbed. By providing a control means for changing the constant, the amount of fuel vapor adsorbed in the canister is estimated from the canister temperature and the engine temperature, and the air-fuel ratio of the internal combustion engine is controlled based on the estimated amount of fuel vapor adsorbed. From doing
Air-fuel ratio control can be performed with high accuracy, air-fuel ratio fluctuations are reduced, emissions are reduced, emissions of harmful air pollutants such as hydrocarbons, carbon monoxide and nitrogen carbide are reduced, and excess fuel is removed from internal combustion. By not supplying the engine, fuel efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a flowchart of air-fuel ratio control.

FIG. 2 is a system configuration diagram of an air-fuel ratio control device.

FIG. 3 is a diagram showing a relationship between a reduced temperature of a canister temperature and an adsorbed amount of evaporated fuel.

FIG. 4 is a flowchart of air-fuel ratio control in a second embodiment.

[Description of Signs] 2 Internal combustion engine 16 Air-fuel ratio control device 20 Evaporation passage 22 Purge passage 24 Canister 26 Evaporation valve 28 Purge valve 30 Canister temperature sensor 32 Intake air temperature sensor 34 Control means

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02D 45/00 312 F02D 45/00 312Q 364 364N F-term (Reference) 3G044 BA01 BA05 BA06 EA03 EA24 EA32 EA42 EA43 FA05 FA09 FA12 FA13 FA14 FA20 FA27 FA32 FA34 GA02 GA03 GA08 GA11 GA22 GA27 3G084 BA09 BA13 BA27 DA02 DA10 DA12 EA07 EA11 EB08 EB11 EC03 FA02 FA05 FA10 FA11 FA18 FA20 FA29 FA33 3G301 HA14 JA02 JA04 JA26 MA01 MA11 NA08 NE02 PA11 PA17Z PB09B PB10B PD03A PE01Z PE08Z PF01Z

Claims (5)

[Claims] An adsorbent adsorbs and retains fuel vapor from the fuel tank between an evaporative passage communicating with a fuel tank and a purge passage communicated with an intake system of an internal combustion engine. A canister for purging the evaporated fuel and supplying a purge gas to the internal combustion engine is provided, and a purge valve is provided in the middle of the purge passage,
An air-fuel ratio control device for an internal combustion engine that controls a purge amount, which is a flow rate of a purge gas to the internal combustion engine, by operating the purge valve according to an operation state of the internal combustion engine, wherein the canister detects a canister temperature state in the canister A temperature detecting means is provided, and an engine temperature detecting means for detecting an engine temperature state of the internal combustion engine is provided, and the internal temperature of the canister based on the canister temperature from the canister temperature detecting means and the engine temperature from the engine temperature detecting means is provided. An air-fuel ratio control device for an internal combustion engine, comprising: control means for calculating an amount of adsorbed fuel vapor and changing an air-fuel ratio control constant according to the calculated amount of fuel vapor adsorbed. 2. The control means changes the air-fuel ratio control basic value itself when the calculated adsorbed amount of evaporative fuel is larger than a set value, while changing the calculated adsorbed amount of evaporative fuel to the set value. 2. The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein a correction value is added to the air-fuel ratio control basic value when the value is smaller than the value. 3. The control means reduces the fuel injection amount when the calculated amount of adsorbed fuel vapor is larger than a set value, while the calculated amount of adsorbed fuel vapor is smaller than the set value. 2. The air-fuel ratio control device for an internal combustion engine according to claim 1, wherein the fuel injection amount is sometimes increased. 4. An adsorbent for adsorbing and holding fuel vapor from the fuel tank between an evaporative passage communicating with a fuel tank and a purge passage communicating with an intake system of an internal combustion engine, and adsorbing and holding the fuel by introducing air. A canister for purging the evaporated fuel and supplying a purge gas to the internal combustion engine is provided, and a purge valve is provided in the middle of the purge passage,
An air-fuel ratio control device for an internal combustion engine that controls a purge amount, which is a flow rate of a purge gas to the internal combustion engine, by operating the purge valve according to an operation state of the internal combustion engine, wherein the canister detects a canister temperature state in the canister A temperature detecting means is provided, and an engine temperature detecting means for detecting an engine temperature state of the internal combustion engine is provided, and the internal temperature of the canister based on the canister temperature from the canister temperature detecting means and the engine temperature from the engine temperature detecting means is provided. A control means for calculating an adsorption amount of the evaporated fuel, changing an air-fuel ratio control constant according to the calculated adsorbed amount of the evaporated fuel, and controlling a purge amount to the internal combustion engine is provided. Control device for an internal combustion engine. 5. The control means increases the purge amount to the internal combustion engine when the calculated amount of adsorbed fuel vapor is larger than a set value, while controlling the calculated amount of adsorbed fuel vapor to the set amount. 5. The air-fuel ratio control device for an internal combustion engine according to claim 4, wherein the purge amount to the internal combustion engine is reduced when the value is smaller than the value.